A diagnosis of hypertrophied adenoid tissue was confirmed in 12 adults each investigated for a nasopharyngeal mass. The patients ranged in age from 17 to 64 and initially presented with either nasal obstruction or serous otitis media. Four patients had evidence of allergic disease. The development of the lymphoid tissue of Waldeyer's ring is reviewed. Although the adenoid is thought to regress in adolescence, it appears that it can remain hypertrophied and become symptomatic in adulthood. A thorough clinical investigation culminating in biopsy is essential to exclude more ominous pathology.